There exist on the market a large number of prosthesis systems for replacing the natural hip joint in the event of painful, traumatic, arthrotic or other changes. Generally, so-called modular systems are used in which there is inserted into a hip socket, which generally comprises a metal alloy, a socket insert which forms a portion of the artificial sliding bearing and which may comprise a metal alloy, a ceramic material, a plastics material or a composite of the above-mentioned materials. The connection between the socket insert and the hip socket is often brought about by means of a so-called conical clamping, wherein a cone-like portion of the external geometry of the socket insert forms a frictionally engaged connection with a correspondingly cone-like portion of the internal geometry of the hip socket, cf. FIG. 1.
FIG. 1 is a sectional illustration of a hip socket (hashed) according to the prior art with an inserted socket insert which is connected to the hip socket via a conical clamping action.
One of the problems which may occur intra-operatively is the skewed insertion of the socket insert into the hip socket. Jamming of the socket insert between three contact points within the clamping cone of the hip socket may then occur in place of the conical clamping described. In accordance with the magnitude of the force applied during clamping, such high frictional forces occur as a result of the point-like jamming that the position of the socket insert can no longer be corrected intra-operatively, cf. FIG. 2.
FIG. 2 is a sectional illustration of a hip socket (hashed) according to the prior art with a socket insert inserted in a skewed manner.
The consequences for the function of the hip joint prosthesis with the socket insert inserted in a pivoted manner substantially depend on the material of the socket insert and range from increased wear and corrosion to complete destruction of the socket insert. For instance, a socket insert inserted in a skewed manner may be the cause of a subsequent complex, painful and expensive revision operation.
In order to prevent the skewed insertion of socket inserts, a range of insertion instruments are commercially available. Their operation is substantially based on the following three steps:                1. Gripping the socket insert at the upper outer edge.        2. Orienting the instrument with the socket insert in relation to the hip socket so that the axes of symmetry of the hip socket and socket insert extend in parallel.        3. Abruptly and rapidly pushing the socket insert into the hip socket, with the gripping retention being disengaged and the clamping connection being produced.        
The upper outer edge of the socket insert is gripped by the instrument generally by means of a so-called three-point fixing arrangement. To that end, the instrument has claw-like elements which project beyond the outer edge of the socket insert at least at three points and apply a normal force or friction force to a point-like location below the front face of the socket insert.
The orientation of the instrument with the socket insert is generally carried out by positioning the instrument on the front face of the hip socket or on elements (for example, recesses or protrusions) near the front face which are again in a plane parallel with the front face.
The abrupt ejection of the socket insert out of the gripper elements, with a clamping action being produced between the socket insert and the hip socket, is generally carried out by an additional ram on the insertion instrument or using a so-called impactor instrument.
Such insertion instruments are described, for example, in EP 1076537 B1 and DE 29922792 U1.
Disadvantages of the existing solutions are as follows:                the insertion of the socket insert into the hip socket and the production of the initial jamming are carried out by a ram or an impactor instrument. Both result in the operating surgeon not having any finger contact with the socket insert and consequently losing some control over the movement of the component. This is generally perceived by surgeons, who establish a substantial portion of their information concerning their operating field by palpation, to be very unpleasant and has a low level of acceptance (=use) for the insertion instruments as a result.        Using an insertion instrument is in most cases an additional operating step which results in a low level of acceptance for the insertion instruments owing to the pressure to increase efficiency in the operating theatre.        Insertion instruments which are supported on the entire front face of the hip socket in order to orientate the socket insert can be impeded during orientation by bone tissue and soft tissue which projects from the outer side over the edge of the hip socket so that it is impossible to insert the socket insert with the instrument without skewing, or the risk of skewing is again increased.        The insertion instrument is often an additional instrument in the set of instruments of the surgeon, which involves additional costs in providing the operating instruments.        Insertion instruments which are not an additional instrument in the set of instruments but which are intended for single use are either supplied as separate products (=additional packaging causes additional time for unpacking and additional waste) or require a specific construction for the packaging of the socket insert in order also to accommodate the insertion instrument therein.        